#include <stdio.h>
#include <string.h>
#include <errno.h>
#include "stdio_impl.h"

void perror(const char *msg)
{
    FILE *f = stderr;
    char *errstr = strerror(errno);

    FLOCK(f);

    /* Save stderr's orientation and encoding rule, since perror is not
     * permitted to change them. */
    void *old_locale = f->locale;
    int old_mode = f->mode;
    
    if (msg && *msg) {
        fwrite(msg, strlen(msg), 1, f);
        fputc(':', f);
        fputc(' ', f);
    }
    fwrite(errstr, strlen(errstr), 1, f);
    fputc('\n', f);

    f->mode = old_mode;
    f->locale = old_locale;

    FUNLOCK(f);
}
